Smart cards are used as subscriber identity modules (SIM) in mobile equipment. In addition to identifying and authorizing the network subscriber, the smart-card module assumes, inter alia, the role of a portable data storage unit for, e.g. call numbers or short messages in the form of text. These short messages are transmitted by the so-called Short Message Service (SMS) and may include up to 160 characters.
As an alternative, the short messages may also be stored in the terminal, but then the advantage of using them in different terminals together with the smart card module is lost.
Since the non-volatile storage space on the smart card module is limited (<16 . . . 32 kByte) and various other data and functions are stored in this memory, the number of short messages that may be saved in this smart card module is limited. It normally lies in the range of approximately 10 to 20. In contrast to the smart card module, there is indeed no technology-dependent upper limits for the size of the memory of the terminal, but even in this case, the economical configuration of the resources of the terminal will lead to limiting the amount of memory for the short messages. In both the smart card module and the terminal, the user has to manually delete the short messages no longer needed when the memory is completely full. A time-consuming sequence of operations is usually required to accomplish this.
Value-added services such as traffic and travel information or mobile banking (account statement) have been offered for some time, in particular by SMS. In connection with such services, the number of short messages received will markedly increase in the future and therefore require increased action on the part of the user to delete short messages.
Since no action by the user is necessary for receiving a short message, the memory may also be filled without the user initially noticing it. In addition, the user may miss perfectly desirable short messages, since no additional message may be received when the memory is completely full.